I have a non-Marketo landing page with four CTAs included throughout the page (Things like "get more information" and "request a live demo"). These CTAs take visitors to four different Marketo pages with forms. The Marketo munchkin is on all of these pages (including the non-Marketo landing page).
If a visitor lands on the non-Marketo landing page from a Facebook or LinkedIn ad, then clicks on one of the four CTAs, and fills out the form on the Marketo landing page, what will the lead source be recorded as? Will it be Facebook or LinkedIn (paid advertisement)? Or will it be the non-Marketo landing page?
There are 2 different notions that are stored in Marketo : the referrer and the lead source.
Since the munchkin is on the non Marketo LP, Marketo will detect the referrer on this first visible page and set it either FaceBook or LinkedIn as the person has arrived from there (Referrers are complete URLs)
For the lead source, things are much more complicated. 2 ways :
There are many, many threads on this topic, so please do a search for them to understand what Gregoire discusses and how to put it together.
Amy, once you've delved deeply into Greg's comments (and Josh's recommendation to get more info via Community search). you might want to devalue (or always clarify) the word "referrer" in your work. I'm not talking here about the conceptual "referring site," but the true HTTP referrer header. The reason is that the referrer is simply not available in many cases. A prime example is when the referring site is served over HTTPS but your site is served over simple HTTP. Even if you had a form capable of reading out the referrer, it wouldn't see anything to read. This security restriction is standard for the modern web.
The above does not apply to the best practice of embedding a source identifier in the URL itself, because that's not technically the referrer, it's just part of the URL. For example, if all the links on LinkedIn have ?source=li, then the destination page can simply read the value of the query param source. This'll work even if someone came from https://linkedin.com to http://www.example.com?source=li. We might still casually call LinkedIn the "referrer" in this case, but I think it's better to call it the link source or similar.